The objective of the proposed project is the anatomical analysis of corticothalamic and thalamocortical connections of the thalamic pulvinar complex. The aim of this analysis is the identification of the specific populations of thalamic neurons which constitute the anatomical substrates for interactions between visual cortex and association cortex. Autoradiography will be employed to demonstrate projections of cortical areas identified by electrophysiological recording. Thalamic neuronal populations recipient of specific cortical inputs will be identified by analysis of the topographic distribution of cortical projections. The distribution of projections back onto cortex from the identified populations of thalamic neurons will be similarly studied with autoradiographic tracing methods. Electronmicroscopy will be employed to evaluate the influence of the cortical projections which converge on given populations of thalamic neurons. Axonal degeneration resulting from lesions to specific cortical areas will be studied electron-microscopically in conventionally prepared and Golgi impregnated tissue to identify postsynaptic structures contacted by identified cortical axon terminals.